A cable television network is a well-known type of communications network that is used to transmit cable television signals and/or other information between one or more service providers and a plurality of subscribers. Most conventional cable television networks comprise hybrid fiber-coaxial (“HFC”) networks that transmit these signals over a combination of fiber optic cables and coaxial cables. In such networks, fiber optic cables are typically used to carry signals from the headend facilities of the service provider to various distribution points, while less expensive coaxial cable may be used, for example, to carry the signals into neighborhoods and/or into individual subscriber premises. In many cases, the proportion of an HFC network that comprises fiber optic cables is increasing. For example, many HFC networks are now implemented as Fiber-to-the Curb (“FTTC”) or as Fiber-to-the-Home (“FTTH”) networks, where the fiber portion of the network may extend down residential streets in the network (in FTTC applications) or all the way to individual subscriber premises (in FTTH) applications.
Typically, the service provider is a cable television company that may have exclusive rights to offer cable television services in a particular geographic area. The subscribers in a cable television network typically pay the service provider to deliver various services to the “subscriber premises” which may include, for example, individual homes, apartments, hotels, businesses, etc. The services offered by the cable television service provider may include, for example, broadcast cable television service, broadband Internet connectivity, and/or Voice-over-Internet Protocol (“VoIP”) digital telephone service. Some customers also receive additional very high data rate services such as video surveillance, very high data rate Internet connectivity and the like. Delivering these services involves transmitting data between the service provider and the subscriber premises. This data is typically delivered to the subscriber premises as radio frequency (“RF”) signals.
RF over Glass (“RFoG”) networks are a particular type of FTTH network. In an RFoG network, fiber optic cables are used to carry analog RF signals that are modulated onto laser beams for transport as optical signals over the fiber optic network infrastructure. These optical signals are then converted back to RF signals at the head-end facilities and at each subscriber premise. One advantage of such systems is that the network infrastructure is transparent to the RF signals, and this allows cable television network operators to continue to deploy the same customer premise equipment that is used in conventional analog HFC networks at each subscriber premise. This customer premise equipment includes set-top boxes, DOCSIS cable modems, and DOCSIS VoIP modems, all of which are in wide use today. The downstream optical signals in an RFoG network (i.e., the signals transmitted from the head-end facilities to the subscriber premises) are transmitted at a nominal wavelength of 1550 nm, and the upstream signals (i.e., the signals transmitted from the subscriber premises to the head-end facilities) are transmitted at a nominal wavelength of 1610 nm.
A Passive Optical Network (“PON”) refers to another type of FTTH network. In a PON network, fiber optic cables are used to carry digital RF signals that are modulated onto laser beams for transport over the fiber optic network infrastructure. As with RFoG networks, in PON networks the network infrastructure is transparent to the RF signals. Conventional PON networks are referred to as 1 GHz PON networks and in such networks the downstream optical signals are transmitted at a nominal wavelength of 1490 nm, and the upstream optical signals are transmitted at a nominal wavelength of 1310 nm. A newer generation of PON networks (referred to as 10 GHz PON networks) is also being introduced. In 10 G PON networks, the downstream optical signals are transmitted at a nominal wavelength of 1577 nm, and the upstream optical signals are transmitted at a nominal wavelength of 1270 nm.
In RF-based FTTH systems such as RFoG and PON networks, optical network units are installed at the subscriber premises and used to convert optical signals that are received from the head-end facilities into RF signals that may be processed by the customer premise equipment, and are also used to convert RF signals that are received from the customer premise equipment into optical signals that are launched onto the fiber optic network for delivery to the head-end facilities. In RFoG networks, these optical network units are commonly referred to as “micronodes” or as RFoG optical network units or “RONUs.” In PON networks, the optical network units that are placed at customer premises are also often referred to as micronodes, although other names may be used. Herein, both RFoG optical network units and PON optical network units will be generically referred to as “micronodes.”
As the optical signals in the above-discussed RFoG, 1 G PON and 10 G PON networks are transmitted in non-overlapping wavelength ranges, the same underlying optical fiber optic network infrastructure may be used to transmit all three types of signals. Consequently, one technique for increasing the bandwidth provided to a subscriber in, for example, an RFoG network is to also transmit data between the subscribe premise and the head-end facilities at one or both of the 1 G PON and/or the 10 G PON wavelengths.